Traditional supra-aural audiometric headphones have had several limitations:
1. Little noise exclusion at low frequencies where background noises are often a problem, when testing in schools or nursing homes, for example;
2. Poor interaural attenuation (cross-head isolation), so that a masking noise must often be used in the non-test ear;
3. A limited bandwidth (6-8 kHz), which makes reliable high-frequency audiometry difficult;
4. An inaccurate real-ear frequency response for speech, so that the spectrum of speech reproduced at the eardrum of the headphone is quite different from the spectrum that would have been produced at the eardrum by the same talker in a face-to-face situation.
5. A headband force that makes the headphones uncomfortable to wear for a long period of time and produces collapsed canals in some older individuals, giving erroneous indications of high-frequency loss. Yet this headband force is still insufficient to produce a seal, giving large test-retest variability at low frequencies.
With the advent of "objective" or ABR (Auditory Brainstem Response) audiometry, which typically uses computer averaging of the minute electrical signals that can be picked up on the head, an additional limitation became apparent:
6. The electromagnetic signal leaking from the headphone is sometimes picked up by the ABR electrodes, causing an artifact in the averaged response.